1. Field of the Invention
The present invention relates to sulfonic acid esters of 2,4,6-tris-(2-hydroxyethoxy)-[1,3,5]triazine and to a positive-working radiation-sensitive mixture, containing
a) as a compound which generates a strong acid under the action of actinic radiation, the sulfonic acid ester PA1 b) a compound having at least one acid-cleavable C--O--C or C--O--Si bond and PA1 c) a polymeric binder which is insoluble in water and soluble or at least swellable in aqueous alkaline solutions. PA1 a) compounds having at least one orthocarboxylic acid ester group and/or carboxylic acid amide-acetal group; these compounds also have a polymeric character and it is possible for the said groups to occur in the main chain or in side chains of the polymer (see DE-A 2,610,842 and 2,928,636), PA1 b) oligomeric or polymeric compounds with recurring acetal and/or ketal groups in the main chain (see DE-A 2,306,248 and 2,718,254), PA1 c) compounds having at least one enol ether group or N-acyliminocarbonate group (see EP-A 0,006,626 and 0,006,627), PA1 d) cyclic acetals or ketals of .beta.-keto esters or .beta.-keto amides (see EP-A 0,202,196), PA1 e) compounds having silyl ether groups (see DE-A 3,544,165 and 3,601,264), PA1 f) compounds having silylenol ether groups (see DE-A 3,730,785 and 3,730,783), PA1 g) monoacetals and monoketals of aldehydes and ketones respectively, having a solubility in the developer between 0.1 and 100 g/l (see DE-A 3,730,787), PA1 h) ethers based on tertiary alcohols (U.S. Pat. No. 4,603,101) and PA1 i) carboxylic acid esters and carbonates whose alcohol component is a tertiary alcohol, an allyl alcohol or a benzyl alcohol (see U.S. Pat. No. 4,491,628 and J. M. Frechet et al., J. Imaging Sci. 30, 59-64 (1986)).
The invention also relates to a radiation-sensitive recording material which is produced from these radiation sensitive mixtures and which is suitable for producing photoresists, electronic components, printing plates or for chemical milling.
2. Description of Related Art
Continuing reduction in the size of the structures, for example down into the range of less than 1 .mu.m in chip manufacture, requires modified lithographic techniques. To form images of such fine structures, radiation of a short wavelength is used, such as high-energy UV light, electron beams and X-rays. The radiation-sensitive mixture must be adapted to short-wave radiation. A compilation of the requirements to be met by the radiation-sensitive mixture is given in the article by C. G. Willson "Organic Resist Materials - Theory and Chemistry" [Introduction to Microlithography, Theory, Materials, and Processing, editors L. F. Thompson, C. G. Willson, M. J. Bowden, ACS Symp. Ser., 219, 87 (1983), American Chemical Society, Washington].
There is therefore an increased demand for radiation-sensitive mixtures which can be used in the more recent technologies, such as mid-UV or deep-UV lithography [exposure, for example, with excimer lasers at wavelengths of 305 nm (XeF), 248 nm (KrF), 193 nm (ArF)], electron beam lithography or X-ray lithography, and which, furthermore, are preferably sensitive in a wide spectral region and correspondingly can also be used in conventional UV lithography.
Mixtures which, in addition to a binder insoluble in water and soluble or at least swellable in aqueous alkaline solutions and a component generating a strong acid under the action of actinic radiation, contain an acid-cleavable compound having, for example, C--O--C or C--O--Si bonds are described, for example, in DE-A 2,306,248 equivalent to U.S. Pat. No. 3,779,778.
Compounds which generate a strong acid on irradiation, especially onium salts, such as diazonium, phosphonium, sulfonium and iodonium salts of non-nucleophilic acids such as HSbF.sub.6, HAsF.sub.6 or HPF.sub.6 as described by J. V. Crivello, Polym. Eng. Sci., 23 (1983) 953 have hitherto been used. In addition, halogen compounds, especially trichloromethyltriazine derivatives or trichloromethyloxadiazole derivatives, o-quinonediazidesulfonyl chlorides, o-quinonediazide-4-sulfonic acid esters, organometal/organohalogen combinations, bis(sulfonyl)diazomethanes, sulfonylcarbonyldiazomethanes (see DE-A 3,930,087) or nitrobenzyl tosylates (see F. M. Houlihan et al., SPIE Proc., Adv. in Resist Techn. and Proc. 920 (1988) 67) have been recommended.
These compounds are used in negative- or positive-working radiation-sensitive mixtures. The use of such photolytic acid generators involves, however, certain disadvantages which drastically restrict the possible uses thereof in various fields of application. For example, many of the onium salts are toxic, and their solubility is inadequate in many solvents, which is why only a few solvents are suitable for preparing a coating solution. Furthermore, when the onium salts are used undesired foreign atoms are sometimes introduced which can cause interference with the process, especially in microlithography. Moreover, the onium salts form Bronstedt acids, which have a very severe corrosive action in the photolysis. These acids attack sensitive substrates, so that the use of such mixtures leads to unsatisfactory results. The halogen compounds and also the quinonediazidesulfonic acid chlorides also form hydrohalic acids which have a severely corrosive action. In addition, such compounds also have only a limited storage life on certain substrates. This was improved by inserting an interlayer between the substrate and the radiation-sensitive layer containing compounds of the type (a), but this led to an undesired increase in defects and to diminished reproducibility, see DE-A 3,621,376 equivalent U.S. Pat. No. 4,840,867.
In more recent papers by F. M. Houlihan et al., SPIE 920, 67 (1988), it was shown by reference to positive-working systems that, in addition to the above-mentioned acid generators, nitrobenzyl tosylates, which on exposure also generate sulfonic acids having a low migration tendency, can be used in certain acid-unstable resist formulations. It can be deduced from these results that such compounds can also be used for photo-curable systems. However, the sensitivities thus achieved and the thermal stability of the photoresists proved to be inadequate.
Resist formulations with naphthoquinone-2-diazide-4-sulfonic acid esters, oximesulfonates, 1,2-disulfones, bis-sulfonyldiazomethane (see DE-A 3,930,086) and sulfonylcarbonyldiazomethane (see DE-A 3,930,087) have also been described. Under the action of actinic radiation, all these compounds form sulfonic acids which do not have a corrosive action. However, the photochemical reaction proceeds with an unsatisfactory quantum yield. The resist formulations absorb radiation of wavelength 248 nm to a considerable degree. The sensitivity to radiation of this wavelength is in the range from 50 to 100 mJ/cm.sup.2. Images of structures having an order of magnitude of 0.5 .mu.m and less cannot be formed by means of such resists.
It is also known from T. Ueno et al., Chemical Amplification Positive Resist Systems Using Novel Sulfonates as Acid Generators, in "Polymers for Microelectronics - Science and Technology", edited by Y. Tabata et al., Kodansha-Weinheim-New York, 1989, pages 66-67 to use 1,2,3-trihydroxybenzene fully esterified with methane-, ethane-, propane-, butane-, benzene-, toluene- or naphthalene-sulfonic acid as a photo-active acid generator in positive-working photoresist systems. However, these resist systems are not used in practice, since their thermal stability and plasma-etching resistance are inadequate and, after development, resist remnants in the grooves and unacceptable resist profiles are observed.
In spite of the intensive research activity so far carried out in this field, no radiation-sensitive mixture is at present known, by means of which a positive-working radiation-sensitive recording material can be produced which has a high sensitivity in the DUV region (200 to 300 nm) and high resolution, and which releases, even on short-time irradiation, a sufficient quantity of an acid which does not have a corrosive action and is strong enough to cleave compounds of type b), and which, in addition, can be developed in aqueous alkaline media.